Spur Gears for Conveyor Systems:
Drive Design and Gear Selection Guide
Steel spur gears power belt, chain, bucket elevator and food processing conveyor drives worldwide. This guide covers module selection, speed ratio calculation, material hardening, plastic spur gear alternatives and mounting — from M2 light-duty to M16 mining head gear.
Module M2 – M16 · AGMA / DIN
0.37 – 400 kW Coverage
Why Spur Gears Dominate Conveyor Drives
The spur gear is the default engineering choice for conveyor drive design — not by convention but by technical logic that holds across virtually every industrial conveyor category. Straight parallel teeth transmit torque between parallel shafts with zero axial thrust, which means the conveyor head pulley shaft bearings only carry radial load from belt tension rather than an additional axial force component that helical gears would impose. This simplifies both the bearing selection and the head pulley mounting arrangement, reducing assembly cost and potential sources of misalignment-induced bearing failure.
Open-gear spur gears on large conveyor head drives — the pinion mounted on the motor gearbox output shaft meshing with a large spur wheel keyed directly to the conveyor head pulley shaft — expose the entire tooth contact zone to visual inspection at every maintenance walkthrough. Unlike enclosed helical gearboxes where deterioration requires either oil analysis or internal inspection, spur gear conveyor drives allow operators to detect pitting, spalling, and tooth tip cracking at a glance. This practical maintainability advantage is commercially significant in bulk materials handling operations where unplanned conveyor stoppages carry production costs that dwarf the cost of the gear itself.
Korea Ever-Power’s spur gears for conveyor drives span module M2 through M16 in C45, 20CrMnTi alloy steel, 316L stainless and engineering plastics — covering the full range from food processing line to open-pit mining conveyor head drive. All steel spur gears for conveyor applications are hobbed and shaved or ground to the specified DIN quality class, with tooth hardening by induction or case carburization matched to the conveyor’s duty cycle and shock loading requirements.
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No Axial Thrust Load
Straight teeth engage parallel shafts with zero axial force component. Conveyor head shaft bearings carry only radial load from belt tension — bearing selection is straightforward, and there is no axial pre-load requirement that would complicate the head pulley mounting arrangement or increase bearing operating temperature.
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Field-Inspectable Tooth Wear
Open-gear spur gears on large conveyor head drives show tooth flank wear, pitting, and root cracking visually at every shift walkthrough. Operators can confirm acceptable wear margins without removing guards or opening gearbox housings — the most practical condition monitoring method available in dusty, wet, outdoor mining and aggregate plant environments.
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Lowest Cost per kW Transmitted
Spur gear hobbing is simpler than helical hobbing and far less expensive than bevel or worm manufacture. For the majority of conveyor drive environments where gear noise is not a primary design constraint — outdoor, mining, aggregate, bulk handling — a spur gear drive consistently delivers the lowest capital cost, lowest maintenance cost, and longest service life per kW of transmitted power among all gear drive types.
FOUR STANDARD SPUR GEAR CONVEYOR DRIVE CONFIGURATIONS
01 — Open Gear Head Drive
Large spur wheel (OD 400–1,200 mm) keyed directly to conveyor head pulley shaft; driven by motor-mounted pinion through an exposed gear mesh. Standard for bucket elevators, cement plant conveyors, grain handling systems and aggregate plant conveyor head drives where enclosed gearbox dimensions and cost are not justified.
02 — Enclosed Spur Gearbox
Cast iron or fabricated steel housing, splash-lubricated ISO VG 220–320 gear oil, flanged to motor and conveyor head shaft coupling. Standard for 2.2–75 kW industrial belt and chain conveyors where dust, weather, or safety regulations exclude open-gear arrangements. Service life 40,000–80,000 hours with correct oil selection and change intervals.
03 — Two-Stage In-Line Reducer
Two spur gear pairs in series within a single cast housing achieve total ratios up to 25:1 — used where motor speed is high and conveyor belt speed is very low, such as precision assembly conveyors, slow slat conveyors for automotive body panels, and temperature-controlled storage conveyors requiring precise indexing speed.
04 — Anti-Runback Backstop
Ratchet or sprag clutch backstop integrated with the spur gear drive on inclined belt conveyors above 10° — prevents the loaded belt from running back under gravity on motor trip or soft-start failure. Standard design requirement for all inclined mining and aggregate conveyors above 5° inclination and all inclined bucket elevator drives.
Module Selection for Conveyor Spur Gear Drives
Module — the ratio of the pitch circle diameter to the tooth count — is the single most important parameter in conveyor spur gear drive design. Module determines tooth size and therefore the load-carrying capacity per unit face width, the centre distance achievable for a given gear ratio, and the pitch line velocity at a given rotational speed. Under-selecting module for a heavy conveyor drive is the most common cause of premature spur gear tooth root fatigue failure; over-selecting increases cost, weight, and centre distance without benefit.
The table below gives Korea Ever-Power’s first-pass module recommendations by conveyor type and power class. These are starting points for preliminary drive layout — full confirmation via Lewis bending stress calculation and AGMA or ISO 6336 pitting resistance calculation at the final design stage is always required for conveyor drives above 7.5 kW or above service factor 1.5.
SPEED RATIO WORKED EXAMPLE — 7.5 kW BELT CONVEYOR AT 1.2 m/s
Head pulley RPM: Belt speed 1.2 m/s, head pulley ∅315 mm → RPM = (1.2 × 60) ÷ (π × 0.315) = 72.8 RPM
Total ratio needed: 4-pole motor 1,450 RPM ÷ 72.8 RPM = 19.9:1 → split into two spur gear stages for compactness
Stage split: Stage 1 = 4.5:1 (20T pinion / 90T wheel); Stage 2 = 4.4:1 (18T / 79T) → total 19.8:1 ✓ — within 1% of target
Module from power: Design power = 7.5 kW × service factor 1.5 = 11.25 kW. Pinion torque at 1,450 RPM = 74 Nm → select M5 C45 induction hardened, 20T pinion, 50 mm face width → root bending stress 138 MPa, within C45 induction hardened allowable 245 MPa ✓
Spur Gear Material and Hardening Selection
C45 Carbon Steel
The standard spur gear material for light and medium belt conveyor drives up to 15 kW. Normalised C45: HB 170–210, allowable bending stress σF = 145–175 MPa, allowable contact stress σH = 520–580 MPa. Induction hardening the tooth flank and root raises surface hardness to HRC 48–54 and increases σH to 900–1,050 MPa, extending conveyor spur gear service life 2–3× vs normalised without the cost and distortion risk of full case carburization. Korea Ever-Power stocks C45 normalised and induction-hardened spur gear blanks in standard modules for fast-turnaround conveyor repair orders.
✓ Best value for indoor M4–M8 belt conveyor
20CrMnTi Alloy Steel
China’s most widely used case-carburizing alloy steel for heavy-duty conveyor spur gears. Case carburization to 0.8–1.5 mm depth followed by quench and low-temperature temper produces: HRC 58–62 tooth surface, σF = 380–430 MPa, σH = 1,400–1,550 MPa. The hard case resists abrasion at mining conveyor pitch line velocities; the ductile core (HB 310–360) absorbs the shock torques of rock-jam events and emergency stops that would fracture a through-hardened gear. Ground to DIN 5–6 for high-speed conveyor pinions above 6 m/s pitch line velocity.
✓ Standard for M8–M16 heavy and mining conveyor
316L Stainless Steel
The material of choice for food processing, dairy, beverage and pharmaceutical conveyor spur gears where daily CIP washdown with NaOH or hypochlorite solution would corrode carbon steel within weeks. 316L with 2–3% molybdenum provides enhanced chloride pitting resistance. HB 160–200, σF = 130–150 MPa — lower than carbon steel; use the next module up from the C45 calculation. NSF H1 food-grade lubricant is compatible. CIP-proof to 85°C NaOH 2% daily. FDA and REACH documentation provided by Korea Ever-Power for food conveyor spur gear orders.
✓ Required for daily CIP washdown conveyor
POM / MC Nylon / UHMWPE
Plastic spur gears for sealed light-duty conveyor drives to 1.5 kW. POM: self-lubricating (μ ≈ 0.10), moisture-stable, FDA-listed, ideal for food and clean-room conveyors. MC Nylon oil-containing grade (green colour): μ ≈ 0.06, higher impact strength than POM, preferred for sealed pharmaceutical and sorting conveyor drives. UHMWPE: lowest friction, immune to virtually all chemical attack, for chemical plant conveyor drives where carbon steel would corrode in weeks.
✓ Food, pharma, chemical conveyor <1.5 kW
Spur Gear Specifications by Conveyor Type
Each major conveyor type creates distinct demands on the spur gear drive in terms of shock loading, environmental exposure, speed, and duty cycle. The following breakdown covers the four most common conveyor categories handled by Korea Ever-Power.
Mounting, Lubrication and Maintenance Intervals
MOUNTING REQUIREMENTS
- →Centre distance: hold to ±0.10 mm for M5 and below; ±0.15 mm for M6–M10 conveyor spur gears
- →Shaft parallelism: ≤ 0.05 mm per 100 mm face width on enclosed conveyor drives
- →Backlash: 0.10–0.30 mm — never eliminate; thermal expansion on heated conveyors causes tooth binding if insufficient clearance is left
- →Bore fit: H7 bore; keyway JS9. Press-fit interference for pinions on shock-loaded conveyor drives above service factor 2.0
LUBRICATION & INSPECTION
- →Open gear (mining/elevator): Bituminous or synthetic open gear compound applied by spray or brush every 250–500 hours of operation
- →Enclosed gearbox: ISO VG 220–320 mineral gear oil; change interval 5,000–8,000 hours; check oil level weekly on mining conveyors
- →Food conveyor: NSF H1 white mineral oil or food-grade PAO; PTFE grease for pitch line velocity < 0.5 m/s
- →Visual inspection: every 500 hours — check for pitting, spalling, scoring on tooth flanks and abnormal noise
- →Replace when: tooth thickness at pitch circle worn >15% of original; conveyor noise increase >5 dB(A) at constant load
Conveyor Spur Gear — Frequently Asked Questions
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